1. Field of the Invention
The present invention relates to a method and apparatus for multiplexing and demultiplexing variable-length high-speed packets, and more particularly, to a method and apparatus for multiplexing a plurality of one-gigabit Ethernet media access control (MAC) frames into a single 10-gigabit Ethernet frame and demultiplexing the single 10-gigabit Ethernet frame into the plurality of one-gigabit Ethernet MAC frames.
2. Description of the Related Art
Packet multiplexing is technology through which a transmitter converts a plurality of packets into a high-speed packet and transmits it to a receiver, and the receiver converts the received high-speed packet into the original plurality of low-speed packets and sent them to a destination.
In realizing such technology, it seems most practical to employ time division multiplexing (TDM) to multiplex low-speed input streams into a high-speed data stream. However, in the case of using TDM, it is necessary to configure a frame such that each input port can be recognized. Moreover, due to the characteristics of TDM, an exclusive channel must be used, which decreases bandwidth efficiency.
To overcome these drawbacks, various conventional methods and apparatuses have been proposed.
In order to multiplex and transmit burst data streams having different lengths, in U.S. Pat. No. 6,009,108 (December, 1999) is disclosed a multiplexing method for converting burst data streams, which have different lengths and are input from different data sources, into a fixed-length packet stream having a constant average transport rate.
In this method, when there is no data having at least the fixed length in a buffer, the data in the buffer is sent to a stuffing data generator to forward stuffing data. Through such operation, the average transport rate of fixed-length packets is maintained constant so that occurrence of buffer overflow and underflow with respect to bursts of data can be reduced in a receiver. However, since packets having a fixed length are generated, an extra conversion device is required for data having a variable length as in the Ethernet. Moreover, in this case, transport efficiency is decreased.
According to U.S. Pat. No. 6,282,211 B1 (August, 2001), transport efficiency is automatically optimized even if a user does not specially request. Here, a channel is dynamically allocated to an available time slot, and a cut-through function is performed within a multiplexer. Accordingly, cost incurred because a user plane is connected to the outside of a multiplexer output part, and a necessary signaling function is performed outside as well as inside, can be reduced.
However, the above-described methods employ conventional TDM channels to transport packets, so bandwidth efficiency is decreased, and the methods cannot be applied to the multiplexing of low-speed Ethernet packets into a high-speed Ethernet packet.
In U.S. Pat. No. 6,269,107 B1 (July, 2001) is disclosed a method of dividing a consecutive data stream into packetized elementary streams (PES) having a fixed length and subdividing a PES into transport streams.
In this method, in order to reduce overhead such as a high-speed circuit which is necessary to process individual packets in series, a plurality of input buffer are provided, and for many input streams having the same characteristic, the result of processing one of the input streams is applied to the other input streams so that a high-speed circuit is not required, and there is no need to separately process individual packets.
Such packet processing method is useful to a case in which a consecutive stream is long and the characteristics of individual packets are the same as in a video signal. However, it is difficult to apply this method to a case in which as in the Ethernet, packets have different lengths and different destinations. Moreover, it is nearly impossible to directly apply this method to a demultiplexer when packet length variation is very large as in the Ethernet.
U.S. Pat. No. 6,262,990 B1 (July, 2001) is provided for multiplexing data (video, audio, and low-speed data) having different speeds whose differences are large, and particularly, low-speed data having a burst characteristic into a fixed-length packet for transmission and for reducing a transmission delay.
In this method, variable-length data of low speed is converted into a fixed-length packet of high speed. However, it is difficult to apply this method to a case in which an output packet also has a variable length as in the Ethernet. Moreover, when a fixed-length packet is generated by stuffing, and a packet of high speed of, for example, 10 gigabits must be processed, a receiver needs to have a function of recognizing and removing the stuffing and reconfiguring the stuffing data into an Ethernet packet.
As described above, conventional TDM methods decrease bandwidth efficiency. Conventional methods of converting and multiplexing data into a fixed-length packet cannot immediately applied to high-speed packets having lengths ranging from 64 bytes to 1522 bytes, but a protocol converter for reconverting the converted high-speed packet into an original Ethernet packet is required together with an extra high-speed switch. In addition, an extra interface circuit for connection to an existing chip set is required.